The most common use of balloon catheters to dilate body passages is angioplasty in which a balloon catheter is used to dilate a coronary artery by collapsing or compressing plaque. Another use for balloon catheters is uroplasty, which is a treatment to relieve urinary obstruction caused by the swelling of the prostate.
The dilatation of the prostatic urethra to treat urethral blockage resulting from benign prostatic hyperplasia has been considered for many years. For example, Guthry in 1830, Ciale in 1841, Mercier in 1850 and Kramer in 1910 all developed metal dilators to unblock urethral obstructions. A good description of the early work in this area can be found in Hinman, F., Jr. (Ed), Benign Prostatic Hypertrophy, Chapter 5, Springer-Valag, 1983. Russinovich et al. utilized a balloon dilatation catheter which was developed for angioplasty by Gruntzig et al. to successfully dilate the prostatic urethra of several male patients which had been partially occluded. (Urologic-Radiology, 2, 33-37, 1980).
For many years, transurethral resections have been commonly performed to remove sections of the prostate gland in order to relieve urinary obstruction at the neck of the bladder and in the prostatic urethra. Uropolasty, on the other hand, involves inserting a balloon into the prostatic urethra and inflating the balloon for a period of time to dilate the prostatic urethra and bladder neck. State of the art balloon catheters for uropolasty generally have such large profiles (transverse dimensions) that relatively large diameter cystoscopic sheaths are required for insertion of the catheter into the patient's urethra. Conventional rigid urological cystoscopes have sheaths with working channels having effective diameters of less than about 5 mm.
The collapsed or deflated balloons of commercially available prostatic balloon dilatation catheters are generally too large to be withdrawn into the working channel of a conventional rigid cystoscopic sheath. For example, it has not heretofore been commercially possible to fabricate a catheter that will fit through the working channel of a rigid cystoscope if the balloon is expanded to form a diameter of approximately 30-35 mm, which is a preferred expansion dimension for the uroplasty procedure. A large balloon size creates the difficulty that even if the non-balloon portion of the catheter body fits into the working channel of the cystoscope, it is very difficult to fold or wrap the balloon to fit through the small working channel. Thus, there has been a need for a balloon catheter in which the balloon can be folded or collapsed more compactly to reduce its deflated profile such that it will fit through the small working channel of conventional cystoscopes.
Effective dilation of the prostatic urethra also requires some means for applying considerable pressure to the urethral wall while maintaining a consistent limit on tissue distension. Further, when a balloon on a dilatation catheter is inflated to dilate a prostatic urethra, the inflated balloon has the tendency to move from the urethra into the bladder. For effective dilatation of the prostatic urethra, the dilatation catheter must be firmly grasped by the physician during the dilation in order to hold the balloon in place and prevent its migration into the bladder. The force on the balloon urging its movement results in significant tensile stresses being applied to the catheter shaft and the juncture between the balloon and the catheter shaft. These high stresses can result in significant extension or even the failure of the shaft or the juncture between the balloon and the shaft. Thus, there has been a need for a balloon catheter which is constructed in such a way that it will withstand the significant tensile stresses being applied during the uroplasty procedure.
What has been needed and heretofore been unavailable is a prostatic dilatation catheter which has sufficiently low shaft and deflated balloon profiles to allow the catheter to be withdrawn through the working channel of a conventional rigid cystoscope and which also has sufficient tensile strength to withstand the tensile stresses imposed upon the catheter during its use. The present invention satisfies these and other needs.